Single channel continuous wave radio control systems can only control one function. One approach used in the past to expand the number of functions controlled is to utilize some sort of modulation of the carrier wave by the transmitter with a decoding of the modulated signal by the receiver to actuate the different functions. This method requires more sophistocated electronics in the transmitter, receiver and control devices with an increase in cost and maintenance of the system. The simplest control signal is the transmission of a continuous wave to indicate that the controlled item is to be in one state and when the continuous wave is no longer transmitted the controlled item reverts to another state.
Methods have been developed to expand this on/off signal to be able to control more than one function. These methods have used an escapement or a cascade of escapements to perform control of several functions. These escapements have typically utilized relays as the actuating mechanism. The use of relays increased the weight and the power drain of the control system.
Other escapements have consisted of a motor to drive the control plates. This motor is in addition to the vehicle drive motor and is best controlled by following pulse-rate and pulse length changes detected by the receiver which adds to the weight, cost and power drain of the control mechanism.